Conventionally, such vehicles as hybrid vehicles have been known to be provided with a plurality of power sources. As one of the vehicles equipped with a plurality of power sources, a vehicle having a secondary battery has been known. In the vehicle equipped with the secondary battery, cells configuring the secondary battery generate heat upon charging and discharging of the battery.
That is, the cells included in the secondary battery have internal resistance in the insides of the cells. Moreover, when the cells included in the secondary battery are connected to one another, it causes contact resistance at connected portions of the cells. Electric currents are passed through the cells having these electrical resistive components, for charging or discharging the cells. When an electric current is passed through each of the cells having the electrical resistive components, the cell generates heat.
By the way, lifetime of the secondary battery is greatly influenced by temperatures. Against such a temperature problem of the secondary battery, the following countermeasures are considered, for example. That is, in normal operation, the cells included in the secondary battery require that airflow be maintained in a predetermined air volume in order to suppress a temperature rise in the cells. Moreover, in operation at very low temperatures, the cells included in the secondary battery require that they be heated in a predetermined quantity of heat in order to exhibit their ability required.
Taking these countermeasures against the temperature problem makes it possible to compute an available power-supply capacity of the secondary battery. In other words, a power supply system using the secondary battery can be improved in capacity of its available power-output, in accordance with what the countermeasures against the temperature problem are. Moreover, the power supply system using the secondary battery can be reduced in the number of the cells that are required for the secondary battery, in accordance with what the countermeasures against the temperature problem are. This means that such countermeasures against the temperature problem are greatly important for the secondary battery.
On the other hand, a vehicle, a means of traveling, has only a limited space to be utilized. In general, in the vehicle using the secondary battery, higher priorities are given to comfort of the passenger cabin, traveling performance of the vehicle, and the like. Accordingly, in the vehicle using the secondary battery, it is difficult to allocate a space large enough to mount the secondary battery. For this reason, in the vehicle using the secondary battery, the vehicle is equipped with the secondary battery the amount of which is restricted because of such an insufficiently allocated space for their mounting.
In the vehicle using the secondary battery, an air-cooling means is commonly adopted to forcibly cool the secondary battery. In the vehicle using the secondary battery, the air-cooling means is used to condition temperature of the secondary battery. A temperature conditioning unit and the like cools the secondary battery, i.e. a member to be temperature-conditioned. As a matter of course, when the output-power density, i.e. energy can be output from the secondary battery on a unit mass basis, becomes higher, it requires a higher output power of the temperature conditioning unit.
Unfortunately, when it is tried to increase the output power of the temperature conditioning unit and the like, it tends to increase the size of the temperature conditioning unit and the like. On the other hand, the members to be mounted in the vehicle are required to be compact, as described above.
In this way, in the vehicle using the secondary battery, compatibility between the following two demands has been required. That is, one of the demands is for a higher output of the temperature conditioning unit and the like, leading to a factor for an increase in size. The other is for downsizing of the members to be mounted in the vehicle.